The present invention relates to transcoding video signals between component and composite forms, and more particularly to an adaptive system which minimizes decoding errors normally associated with decoding the composite signal.
Heretofore it has been common practice to generate and process composite video signals throughout the entire television studio. However, for sophisticated signal processing applications, e.g., geometric special effects, such as rotation and changes in size, it has been found that it is best to process the individual video component signals (Y, I, Q or R, G, B, etc.), since the frequency and phase of the color subcarrier will change during said processing of the composite signal, which subcarrier is not present in a component system. Further, it is highly possible that the standards ultimately adopted for digital video will comprise both component and composite formats. Of course, component video signals must be reassembled into composite form to conform to NTSC or any other standard presently permitted before being broadcast. Unfortunately, present systems of transcoding from component to composite video and vice versa cause errors due to the inability to perfectly separate luminance (Y) and chroma (I and Q) components from a composite signal.
In particular, the problem is caused by the overlapping frequency spectrums of the luminance and chroma signals. Low-pass ang band-pass filters do a poor job of separation due to said overlapping spectrum. Comb filtering does a better job in that high frequency horizontal luminance resolution is preserved and separated from the chroma signal, but provides poor vertical resolution. Thus both types of filters result in some type of crosstalk between channels.
It is therefore an object of the invention to provide a system capable of transcoding between composite and component video signals and vice versa with a minimum of crosstalk.